The invention relates, generally, to storage vessels for cryogenic liquids and, more particularly, to an improved support system for such vessels.
The typical cryogenic storage vessel is shown in FIG. 1 and consists of an inner tank 3 for retaining a supply of cryogenic liquid. Surrounding the inner tank is an outer jacket 5. The outer jacket 5 is supported so as to be spaced from the inner tank thereby to create an insulation chamber 7 therebetween. The insulation chamber is filled with an insulating material, for example, sheets of super insulation wrapped around the inner tank, and a vacuum is created therein. The vacuum and insulating material minimize both radiant and conductive heat transfer to the interior of the inner tank, thereby to minimize vaporization of the cryogenic liquid stored therein.
As shown in FIG. 1, the typical tank includes a fill line 9 for delivering the cryogen to the tank, a delivery line 11 for delivering cryogen from the tank and a vent line 13. These lines run from the exterior of the vessel through the insulation chamber and into the tank. As will be apparent, these lines conduct heat from the external environment to the cryogen in tank 3. To minimize the inleak of heat to the tank, it is desirable to make the length of the pipes located in the insulating chamber 7 as long as possible thereby to make the heat path as long as possible. In the prior art this was accomplished by making the inner tank 3 relatively short as compared to the outer jacket 5 so as to create a wide insulation chamber in the area where the pipes penetrate the tank and jacket as shown at 17 and 19 in FIG. 1.
While such an arrangement minimizes the heat transferred through the pipes to the cryogen in the tank, it substantially reduces the capacity of the inner tank 3 as compared to the size of the outer jacket 5. It is also necessary to insulate the relatively larger area between the tank and jacket thereby increasing manufacturing costs. Moreover, because the lines exit the tank at various points on the jacket 5, extensive plumbing is required to connect these lines to the various valves, regulators and pipes for use.
Also illustrated in FIG. 1 is the prior art system for communicating a liquid level sensor with the liquid in the vessel. Typically, a pathway is created between the exterior of the vessel and the inner tank 3 by a conduit 21. A level sensor passes through conduit 21 to measure the level of the liquid cryogen. Conduit 21 creates a very short heat path between the inner tank 3 and external environment. As a result, significant, undesirable heat transfer occurs between external environment and the liquid cryogen in tank 3.
Thus, an improved support system for a cryogenic vessel is desired.